Problem 1001: Sum Problem

Thanks to drizzlecrj's suggestion, I turned to hdu for the primary practice. Hnu was another choice, but the server is too poor that a submitted problem is showed "wariting" all the time.

Problem Description

Hey, welcome to HDOJ(Hangzhou Dianzi University Online Judge).

In this problem, your task is to calculate SUM(n) = 1 + 2 + 3 + ... + n.

Input

The input will consist of a series of integers n, one integer per line.

Output

For each case, output SUM(n) in one line, followed by a blank line. You may assume the result will be in the range of 32-bit signed integer.

Sample Input

1
100

Sample Output

1
5050

#include <stdio.h>

int main()
}

Summary:
Easy as it may seem, I am starting off.